To meet the challenge of rising costs of laboratory diagnostics associated with prevalent diseases, such as cardiovascular disease, cancer, diabetes, HIV, etc., a new technology is emerging called “Lab-on-a-Chip (LOC).” LOC implements one or more biochemical laboratory protocols or assays on a small chip (e.g., one of a few square centimeters in area). Compared with traditional bench-top procedures, these biochips offer many advantages, namely low sample and reagent consumption, less likelihood of error due to minimal human intervention, high throughput and high sensitivity.
One example biochip, called a “digital microfluidic (DMF) biochip”, is designed to integrate assay operations such as detection, as well as sample pre-treatment and sample preparation on one chip. Front-end diagnostic functions, such as dilution of a sample, can be carried out on-chip or by pre-processing during sample preparation outside the chip. Off-chip sample processing and sample preparation may pose a significant hindrance to the overall biochemical assay completion time, due to long lead times that may be required for laboratory processes. Therefore, it may be desired that for fast and high throughput applications, sample pre-processing steps, such as sample dilution, be automated on-chip, i.e., integrated and self-contained on the biochip itself.
One challenge associated with using digital microfluidic biochips for diluting samples/reagents is to use dilution schemes that both minimize waste and require a relatively small number of dilution steps to achieve the desired target concentration.